1. Field of the Invention
The present invention relates to an inkjet recording device and an ink supplying device employed thereby.
2. Description of Related Art
Line scanning type inkjet printers have been proposed as high-speed inkjet printers for printing on continuous recording paper at high speeds. These devices have a page-width long recording head spanning the entire width of a continuous recording paper and formed with rows of nozzle holes from which ink particles are ejected. This page-width line recording head is positioned opposite the recording paper and is selectively controlled according to recording signals to deposit ink particles ejected from the nozzle holes onto the recording paper. At the same time, a main scanning process is performed by moving the recording paper at a high speed in the lengthwise direction of the continuous recording paper. An image is formed on the recording paper by controlling the main scanning process and the deposition of ink particles to form recording dots.
Many examples of line scanning type inkjet printers have been proposed to date, such as devices that include a recording head employing a continuous inkjet system and devices that include a recording head employing an on-demand inkjet system. While the on-demand type line scanning inkjet printers cannot equal the recording rate of devices using the continuous inkjet system, the on-demand inkjet system has proved suitable for use in high-speed printers that are in widespread use, due to the simple construction of the ink system and the like.
The recording head in line scanning inkjet printers using the on-demand inkjet system is a line-type recording head in which a plurality of nozzles is provided in rows. The nozzle holes serve as openings to an ink chamber filled with ink. Ink particles can be ejected via the nozzle holes by applying a drive voltage to piezoelectric elements or heat elements to increase pressure in the ink. An ink supplying device is connected to this recording head for supplying ink to the each nozzle.
When supplying ink from the ink supplying device into the recording head, the ink includes air bubbles that remain in the ink chamber. When pressure is applied to ink in the ink chamber in which residual air bubbles exist, volume changes in the ink chamber are absorbed by the contraction of these residual air bubbles, resulting in improper ejection of ink droplets from the nozzle holes and unsatisfactory recording quality. The problem of residual air bubbles is more serious in line-type inkjet printers than in serial printers because line-type inkjet printers are provided with numerous nozzles and perform one-pass recording.
Conventional methods for overcoming these problems include a first filling method employing the capillary effect and the wettability of material contacted by the ink to eliminate flow stagnant areas in the ink channel and to introduce ink free from residual air bubbles, or this method combined with a purge process. A method using the capillary effect used above is disclosed in Japanese patent-application publication (Kokai) No. HEI-11-227228, while a method using the wettability of material contacted by ink is disclosed in Japanese patent-application publication (Kokai) No. HEI-7-223322. A method for eliminating flow stagnant areas in the ink channels is disclosed in Japanese patent-application publication (Kokai) No. HEI-7-195685.
A second filling method expected to achieve further improvements is disclosed in Japanese patent-application publication (Kokai) No. SHO-56-113464. In this method, the recording head and ink channels in the ink supplying device are evacuated prior to replacing the space with ink.
However, line scanning type inkjet printers employ long recording heads with numerous nozzles. Further, since sufficient ink must be supplied to these numerous nozzles, the ink supplying channels must be wider in diameter. In addition, the ink supplying channels tend to become complex in construction. Accordingly, when applying the first filling method to a line scanning type inkjet printer, it is difficult to fill the channels with ink free from residual air bubbles.
While improvements have been made in the second filling method, this method is still insufficient for line scanning type inkjet printers. Problems have arisen particularly in the process of filling the recording device with ink after assembly, due to some problems in the initial filling stage. Further, when attempting to refill the recording device a second time, it is more difficult to raise the vacuum level in the various components, requiring more time. The success rate for refilling the recording device a second time tends to be lower than that of the first filling attempt. Further, when refilling the recording device during short interims between print jobs, during maintenance, or the like and then attempting to resume a recording operation immediately, filling the device satisfactorily with ink free from residual air bubbles has proven to be even more difficult. In addition, the nozzle holes occasionally become clogged during the ink refilling process.
In view of the foregoing, it is an object of the present invention to provide an inkjet recording device and an ink supplying device employed by the inkjet recording device that are capable of filling the recording head and ink supply channels with ink free from residual air bubbles reliably and within a short amount of time, thereby making it possible to resume highly reliable recording operations quickly, even in line scanning type inkjet printers having numerous nozzles and complex ink supply channels that are long and wide in diameter.
In order to attain the above and other objects, the present invention provides an inkjet recording device. The inkjet recording device includes an ink reservoir that stores ink, a recording head having a plurality of nozzle holes for forming recording dots on a recording medium by ejecting ink particles from the plurality of nozzle holes onto the recording medium positioned opposite the plurality of nozzle holes, an ink channel for supplying ink from the ink reservoir to the recording head, ink discharging means for discharging ink from the recording head and the ink channel, evacuating means for creating a vacuum state in the recording head and the ink channel, and ink filling means for filling the evacuated recording head and ink channel with deaerated ink, wherein the ink discharging means divides the recording head and the ink channel into a plurality of sections and independently discharges ink from each section of the recording head and the ink channel.
The present invention also provides an inkjet recording device. The inkjet recording device includes an ink reservoir that stores ink, a recording head having a plurality of nozzle holes for forming recording dots on a recording medium by ejecting ink particles from the plurality of nozzle holes onto the recording medium positioned opposite the plurality of nozzle holes, an ink channel for supplying ink from the ink reservoir to the recording head, ink discharging means for discharging ink from the recording head and the ink channel, evacuating means for creating a vacuum state in the recording head and the ink channel, and ink filling means for filling the evacuated recording head and ink channel with deaerated ink, wherein the ink discharging means includes external air introducing means introducing external air into the ink channel.
The present invention also provides an ink supplying device. The ink supplying device is used for an inkjet recording device having a recording head. The ink supplying device selectively supplies one of a plurality of types of ink to the recording head. The ink supplying device includes for each of the plurality of types of ink an ink channel for supplying ink to the recording head, ink discharging means for discharging ink from the recording head and the ink channel, evacuating means for creating a vacuum state in the recording head and the ink channel, and ink filling means for filling the evacuated recording head and ink channel with deaerated ink, wherein the ink discharging means comprises external air introducing means introducing external air into the ink channel.